This invention relates to an improved toggle bolt assembly that is insertable through a clearance hole formed in a hollow wall and, in particular, to a thin flexible locking strip that is looped over the bolt to lock the wings of the trunnion nut in a non-rotatable unfolded condition inside the hollow wall. As disclosed by Giannuzzi in U.S. Pat. No. 4,616,968, one problem associated with most toggle bolt assemblies relates to the fact that the winged trunnion nut is free to rotate with the bolt after it has passed into the wall. In order to prevent rotation, the bolt and the fixture attached thereto are generally pulled away from the wall to anchor the extended or unfolded wings against the back of the wall. While applying back pressure to the bolt, the operator must turn the bolt forward into the now retained trunnion nut while at the same time supporting the weight of the fixture. This can oftentimes prove to be a difficult and dangerous operation particularly where the worker is using a power tool to drive the bolt home. It is further noted that toggle bolts also tend to become loosened where subject to vibrations thereby releasing the attached fixture from the wall.
Giannuzzi solves the problems noted in the prior art by incorporating a wire locking device in a toggle bolt assembly. The wire device is wound about one of the nut trunnions. One end of the coil has a short tail that extends under a wing of the nut unit. The other end of the coil has a longer tail that terminates in a compressible loop. The loop, in assembly, is compressed inside the clearance hole alongside the bolt and serves to hold the winged trunnion nut against rotation. Accordingly, the head of the bolt and the fixture captured thereunder can be conveniently supported against the outside of the wall while the bolt is being driven home. Once tightened down, the bolt is prevented from loosening by the holding power of the wire locking coil.
The Giannuzzi device functions quite well to lock the winged trunnion nut of a toggle assembly against rotation. However, the device has certain disadvantages that make it difficult to use in the field. The wire locking coil must be wrapped about one of the trunnions during manufacture of the winged nut unit thus raising considerably the unit price of the assembly. The locking device must act in concert with the toggle spring to insure proper extension of the wings. The locking coil also is formed of metal, which in many applications is exposed to moisture. The exposed coils under these conditions will corrode and eventually fail whereupon the bolt can work loose of the nut. The compressible loop of the locking device must be located inside the bolt clearance hole alongside the bolt shank. As a consequence, the coil can be either broken or driven out of the hole by the turning screw threads. The locking device of the Giannuzzi assembly as noted is made of thin wire with the compressible loop cantilevered from the main coil by a long thin wire tail which is easily bent or otherwise damaged during handling or shipping. Here again, any damage to the delicate tail will typically render the device unusable.